There are two proofs which I have attempted to work on that have beein somewhat trifling. The first of which is :(adsbygoogle = window.adsbygoogle || []).push({});

prove that the function f: [0,infin) -> R defined by f(x) = 1/x is not uniformly continuous on (0,infin).

im thinking that the way in which i should probably attempt to solve this problem is by using a theorem which states:

for a function f: D -> R and a point x_0 in its domain D, the following two assertions are equiv:

i.) the function f: D -> R is contin. on x_0

ii.) for each epsilon > 0, there exists a delta > 0 such that |f(x) - f(y)| < epsilon for all points x in D such that | x - x_0 | < delta

I suppose that if i were to do that then all i would have to do is let x_0 be a point at infinity (in the domain) and allow x to converge to x_0? then somewhere, somehow, something equals zero which is not strictly greater than epsilon (or something along these lines maybe?) also, would it perhaps be easier to solve this proof by contradiction and if so, how would one venture into doing so?

=======================

second proof: prove that g: [0, infin) -> R defined by g(x) = (4x) / (x+2) is uniformly continuous on [0, infin).

after finding a common denom. for | g(x) - g(y) | < epsilon, this resolves to ( 8 |x-y| ) / ( |x+2| |y+2|) the |x-y| in the numerator can be swapped out for a delta, but im kind of stuck after this. what should i do next and what steps am i leaving out?

While i understand pretty much everything i read it's only a small portion of what's required for a math analysis course (as most of you know). But im very weak in the area of actually preforming a proof - once i see the direction it's taking, however, i can usually do okay, but the initial steps always give me trouble. I've had the usual basic introduction to continuous functions and limits as well as sequences - everything you usually learn in your first math/calculus analysis course. While i understand the principle of proofs (and even forward-backward techniques) im still just very weak at actually doing them (for lack of experience). so with all of that having been said, any help would be greatly appreciated.

thank you !!!!!

**Physics Forums - The Fusion of Science and Community**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Calc Proof(s): Uniform Continuity

Loading...

Similar Threads for Calc Proof Uniform | Date |
---|---|

Question about area between curves (integral calc textbook q | Aug 4, 2017 |

I Which topics from precalc are essential for calc 3? | Jan 13, 2017 |

Helpful Resources for Calc. Analysis | Sep 17, 2015 |

Math methods in physics book - vector calc proof | Jan 14, 2013 |

Vector calc proof question | Sep 22, 2008 |

**Physics Forums - The Fusion of Science and Community**